A sex attacker who targeted women in Oxford was jailed yesterday after being branded a "dangerous offender" by a judge.

John Cassidy attacked four lone women in secluded spots in the city during a five-day spree last year.

Neighbours and women's groups welcomed the prison sentence and said the victims had suffered a "traumatic ordeal".

Cassidy, 27, of Samphire Road, Blackbird Leys, appeared at Oxford Crown Court and admitted two charges of sexual assault and one of indecent exposure.

He asked for a second indecent exposure incident to be taken into account.

Judge Mary Jane Mowat sent him to jail for an "indefinite period", but said that he should spend at least three years under lock and key.

She said: "I regard you as a dangerous offender. The lady you knocked off her bike described it as the worst experience of her life.

"You pose a significant risk to members of the public."

Chris Badger, prosecuting, said the attacks took place in Reliance Way and Marsh Park, in Cowley, as well as on a cycle path near South Parks Road, in the city centre, last November.

The court heard Cassidy had six previous convictions for similar attacks and had served three-year and six-year sentences for sexual assault during the 1990s.

Mr Badger said the latest series of incidents began on November 11, when Cassidy exposed himself to two women in Reliance Way.

The following evening, Cassidy groped a cyclist in the same street as she placed a lock on her bike.

Two days later, he exposed himself before committing an indecent act in front of a dog-walker in Marsh Park, Cowley.

Then on November 16, Cassidy pushed a cyclist to the ground between Ferry Road and South Parks Road. He grabbed her mouth and groped her before gripping her neck. When a passer-by appeared, Cassidy pretended the girl had fallen off her bike, before he ran off.

Jonathan Coode, defending, said Cassidy needed a rehabilitation course in the community.

But Judge Mowat said: "What you do has always been the same - targeting women alone in public places like parks or pathways, approaching them, exposing yourself, attacking them, more or less violently, according to their circumstances and their reaction.

"Nothing has changed. Whatever he may protest, it would appear he cannot help himself attacking women. It's compulsive.

"He's dangerous, because of his previous sexual offences, and it would be completely unreasonable to argue otherwise."

A 58-year-old woman, from Samphire Road, who did not want to be named, said: "This kind of thing isn't nice. There must be something wrong with someone who wants women to feel vulnerable.

"It starts with flashing someone, but where does it end?"

A volunteer from the Oxford Sexual Abuse and Rape Crisis Centre said: "Women who have been attacked like this will be glad he's out of the way."

Thames Valley Police spokesman Kate Smith said: "Indecent exposures can be upsetting and frightening and these sexual assaults were particularly harrowing and traumatic ordeals for the victims."